PDBsum entry 1gfp

Transmembrane protein

PDB id

1gfp

Contents

			Protein chain

					340 a.a.

			Ligands

					C8E ×12

			Waters ×149

References listed in PDB file

Key reference

Title

Structural and functional characterization of ompf porin mutants selected for larger pore size. I. Crystallographic analysis.

Authors

K.L.Lou, N.Saint, A.Prilipov, G.Rummel, S.A.Benson, J.P.Rosenbusch, T.Schirmer.

Ref.

J Biol Chem, 1996, 271, 20669-20675. [DOI no: 10.1074/jbc.271.34.20676]

PubMed id

8702816

Abstract

OmpF porin is a nonspecific pore protein from the outer membrane of Escherichia coli. Previously, a set of mutants was selected that allow the passage of long maltodextrins that do not translocate through the wild-type pore. Here, we describe the crystal structures of four point mutants and one deletion mutant from this set; their functional characterization is reported in the accompanying paper (Saint, N., Lou, K.-L., Widmer, C., Luckey, M., Schirmer, T., Rosenbusch, J. P. (1996) J. Biol. Chem. 271, 20676-20680). All mutations have a local effect on the structure of the pore constriction and result in a larger pore cross-section. Substitution of each of the three closely packed arginine residues at the pore constriction (Arg-42, Arg-82, and Arg-132) by shorter uncharged residues causes rearrangement of the adjacent basic residues. This demonstrates mutual stabilization of these residues in the wild-type porin. Deletion of six residues from the internal loop (Delta109-114) results in disorder of seven adjacent residues but does not alter the structure of the beta-barrel framework. Thus, the large hollow beta-barrel motif can be regarded as an autonomous structure.



	Figure 3. Fig. 3. Stereo diagram of the model of porin mutant R42C with partial wild-type model superimposed. Only those side chains of the wild-type model that differ significantly from the mutant model (Arg-42 and Arg-82) are shown (in brown). The view is similar to that in Fig. 1.		Figure 4. Fig. 4. Stereo diagrams of porin mutant R82C. a, 2F[o] F[c] electron density (contoured at 1 ) with model superimposed. b, model of R82C with partial wild-type model superimposed. Only those side chains of the wild-type model that differ significantly from the mutant model (Arg-42, Lys-80, Arg-82, and Arg-132) are shown (in brown). Both conformations of Lys-80 are shown (see text). Magenta, major conformation with side chain amino group forming a salt-bridge with Cys-82 (see also a); yellow, minor conformation.